Continuity mistake: When the Riffian finds Stan and Oliver in the store cupboard, he stands on some tacks and you can see he drops his knife in the process, but when we see the Riffian a few seconds later, the knife is now back in his hand.

Continuity mistake: When Stan and Oliver escape from the Riffian in the store cupboard, Oliver knocks over a barrel of tacks on the floor and you can see that the barrel is facing left, but in the next shot it is now facing right.

Continuity mistake: When Stan pulls the door into Oliver's face, Oliver falls backwards and the spring on his back sends him skywards and onto the piano. When Oliver falls onto the piano, you can see that there is nothing on his stomach, but a few seconds later he is covered with piano hammers and other parts from the interior of a real piano.